Portable data carrier assembly comprising a security device

ABSTRACT

The invention relates to a portable data carrier system having a control unit, a body, a data memory integrated in a chip, in which security-relevant data can be stored, and a means feature for permitting information exchange between the control unit and an external access unit. A security device of the chip transmits a security signal that is influenced by an influencing means feature integrated in the body and non-electrically connected with the security device. A detection means feature of the security device detects the influenced security signal, an evaluation means feature evaluates the detected, influenced security signal, and a blocking means feature blocks a security-critical operating state of the data carrier system if the evaluation means feature does not recognize a security signal influenced in the expected way.

[0001] This invention relates to a data carrier system having a controlunit, data memory, a body giving the data carrier system its externalform, and means for permitting information exchange between the controlunit and an external access unit.

[0002] Such data carrier systems are known for example in the form ofcontact-type or contactless chip cards, security labels, luggage labelsor vehicle keys. The control unit, data memory and part of the means forpermitting information exchange are usually integrated on a chip in theform of an electronic circuit. Information exchange can be effected forexample via external contacts or via inductive or capacitive antennaswith a corresponding transponder device.

[0003] External access units transmit and receive information to andfrom the data carrier system and frequently also supply it with energy.They are usually referred to as readers despite the possibility ofbidirectional communication.

[0004] Certain data carrier systems, such as cash cards, access cards orvehicle keys for activating the driving mode, deactivating immobilizersor actuating locking systems, involve the storage of security-relevantdata, such as secret key data. Due to encrypted storage, suchsecurity-relevant data cannot be spied out as long as the electroniccircuit configuration of the chip is not in the operating state. Anattack on the security-relevant data stored in a chip consequentlyrequires that the electronic circuit configuration of the chip is in theoperating state and the security-relevant data are stored in decryptedform.

[0005] Secret data in a data carrier system can be attacked via theexternal contacts of a contact-type data carrier system or via the radiolink of a contactless data carrier system. However, there are quite afew measures not explained in any detail here for preventing suchattacks from permitting access to secret key data or othersecurity-relevant data. A further possibility for spying out data is toattack the chip, for example by using focused ion beams or electronmicroscopy to determine the charge state of memory cells or the dataflow on data buses. Such an attack on the chip usually requires removalof the chip or at least of a chip module with chip and contacts ortrans-transponder antenna from the card. For this purpose the card isusually greatly damaged or the card material chemically dissolved.

[0006] German laid-open print DE 197 38 990 A1 discloses a chip cardhaving a security device containing an oscillator for transmitting asecurity signal. The signal emitted by the oscillator is excited by acapacitance arrangement which is part of the module and produces a valuethat is characteristic of the sensed capacitance. Said signal isdetected with a detection means, evaluated by an evaluation means, andthe function of the card is enabled when the sensed capacitance matchesthe chip-specific capacitance.

[0007] The problem of the invention is to provide a data carrier systemof the abovementioned kind that impedes attacks on the chip of said datacarrier system when in the operating state.

[0008] This problem is solved by a portable data carrier system having acontrol unit, a body giving the data carrier system its form, a datamemory integrated in a chip, in which security-relevant data can bestored, and means for permitting information exchange between thecontrol unit and an external access unit. According to the invention,such a data carrier system has a security device for delivering asecurity signal, and an influencing means integrated in the body andnon-electrically connected with the security device for influencing thesecurity signal. Furthermore, the security device has a detection meansfor detecting the security signal influenced by the influencing means.An evaluation means is provided for evaluating the detected, influencedsecurity signal. A blocking means blocks a security-critical operatingstate of the data carrier system if the evaluation means does notrecognize a security signal influenced in the expected way.

[0009] The blocking of a security-critical operating state of the datacarrier system can be for example the closing of an active program, thepreventing of a program start or the erasure of a memory containingsecurity-relevant data.

[0010] The control unit of an inventive data carrier system can be alogic circuit for realizing predetermined operations. Likewise, it canbe a microcomputer or microcontroller with corresponding controlsoftware. The body of the data carrier system can have for example theform of a chip card or a key. However, it can also have any other formthat can preferably be carried comfortably, such as jewelry to be wornon the body, a key pendant or a security label. Suitable jewelry to beworn on the body could be designed e.g. in the form of a ring, awristwatch, a pendant or a brooch.

[0011] Means for permitting information exchange between the controlunit and an external access unit can be e.g. a signal input/outputdevice with a contact surface arrangement, or else a signal input/outputdevice with a contactless coupling device, such as an inductive orcapacitive coupling arrangement or a radio antenna.

[0012] Generic data carrier systems in the form of a chip card are knownfor example from Wolfgang Rankl/Wolfgang Effing, Handbuch derChipkarten, 3^(rd) edition, Carl Hansa Verlag, 1999. This book describesin particular the principles of memory cards, microprocessor cards andcontactless chip cards, signal input/output devices with contacts andsignal input/output devices for contactless cards.

[0013] Generic contactless data carrier systems of different designs areexplained in detail in Klaus Finkenzeller, RFID-Handbuch, 2^(nd)edition, Carl Hansa Verlag, 2000.

[0014] The inventive security device for transmitting a security signaland the corresponding influencing means for influencing the securitysignal are greatly dependent on each other and adjusted to each other.The special feature of the security device and the influencing means isthat during operation of the control unit of a data carrier system it ispossible to check whether the card body or at least the influencingmeans is in the proximity of, or actually in a certain spatialconstellation relative to, the security device and thus the data memory.The transmitting power of the security device can be extremely low,since the influencing means can be disposed very closely adjacent to thesecurity device or the signal coupling device thereof.

[0015] In a development of an inventive data carrier system, theinfluencing means provided is a transponder. In particular, theabovementioned “RFID-Handbuch” discloses a great number of differenttransponders in so-called RFID systems (from the English term “RadioFrequency IDentification”). The technical relations between transponderand reader holding for such RFID systems, such as coupling, energytransfer, signal transmission, signal evaluation, etc., are alsoapplicable to transponders according to the present invention. A greatdifference between known transponders and a transponder according to thepresent invention is that a prior art transponder is a data carriersystem communicating with a stationary reader. Such a transponder can bea generic data carrier system, as mentioned above.

[0016] A transponder of an inventive data carrier system is not providedfor communication with a reader disposed outside the body of the datacarrier system but for interaction with a security device disposedwithin the data carrier system and having at least partly thefunctionality of a reader with respect to the transponder. A transponderin an inventive data carrier system thus forms together with a securitydevice an RFID system within the data carrier system. Since such asystem is to be used for protecting a chip from unauthorized attacks,the stated security device is preferably integrated at least partly inthe chip to be protected.

[0017] One of the special features of an inventive RFID system withinthe data carrier system is that the short distance within the datacarrier system body permits the transmitting power to be very low andalso coupling antennas or coils to be very small. On the other hand, thesecurity device should preferably not be too complicated in structureand the energy consumption of the RFID system should preferably be low.Also, a transponder should be very small and preferably inexpensive.With consideration of these requirements, an inventive data carriersystem can use for its security device and influencing means largely alltechnologies described in the pertinent literature. For example, aso-called 1-bit transponder can be used, which can only transfer theinformation “transponder present” or “transponder not present.”

[0018] Additional information on the spatial arrangement of thetransponder relative to the security device can in this case be derivedfrom coupling-dependent information components of security informationreceived by the detector device from the transponder. Furthermore, theRFID system within the data carrier system can work on a so-calledradiofrequency method by which a resonant circuit is used as atransponder and the signal frequency of a security signal delivered bythe security device and the resonance frequency of such a resonantcircuit are adjusted to each other. The signal frequency of the securitysignal is preferably adapted to the actual resonance frequency of theresonant circuit, so that the transponder can be fabricated as amass-produced article without calibration. If a fixed signal frequencyis used, the resonance frequency of such a transponder arrangement thatis effective for the security device can nevertheless be calibrated by avariable capacitance integrated in the security device. For thispurpose, such a variable capacitance must be provided as part of aresonant circuit circuit loading the signal output of the securitydevice and realized using a transponder arrangement.

[0019] Also, an influencing means of an inventive data carrier systemcan consist of a dipole with a nonlinear active element to form, inknown fashion, harmonics of a microwave signal delivered by the securitydevice, which can be evaluated by an evaluation means. In addition, theinfluencing means can cause the load modulation of a security signaldelivered by a security device, such as in particular resistive loadmodulation or capacitive load modulation. Furthermore, the influencingmeans can be an antenna and an electronic circuit, the circuitconfiguration changing the load resistance of the antenna to modulatethe reflection cross section (“modulated backscatter”). A securitydevice in this case transmits a signal and detects the modulated signaltransmitted back by the influencing means. If the modulation is suitablysignificant for the presence of the intact influencing means, anevaluation unit can recognize the absence of such an influencing means.If the signal amplitude of the reflected security signal, possiblyadditionally depending on different signal amplitudes of the securitysignal delivered by the security device, is used as a further criterionfor the presence of the influencing means, an evaluation means of such adata carrier system will recognize with a very high degree of certaintythat the data carrier system has been tampered with.

[0020] A simple embodiment of a passive influencing means can be forexample a component with a complex impedance, i.e. a capacitance orinductance as part of a resonant circuit or else an independent resonantcircuit. Such an impedance or resonant circuit can be provided forexample by inductive or capacitive coupling as the load impedance of aradiofrequency signal generator of the security device. A relative shiftof inductive coupling coils of the security device and the influencingmeans or a relative shift of electroconductive surfaces acting ascapacitor plates of the security device and the influencing means leadsto a change of coupling factor, a change of quality of such a resonantcircuit and a change of resonance frequency.

[0021] The signal level of a radiofrequency generator loaded by aresonant circuit depends in nonlinear fashion on the output frequency ofthe radiofrequency generator or or on the offset of said outputfrequency of the radiofrequency generator from the resonance frequencyof the resonant circuit. When the security device delivers outputsignals with different frequencies in the range of the resonancefrequency of the resonant circuit, a detector device will determine apredictable signal level in dependence on the signal frequency withincertain limits with a proper constellation of security device andinfluencing means. When e.g. two security signal frequencies areoutputted that both deviate from the resonance frequency on the sameside, the difference of the detectable output signal levels of the twofrequencies will be largely the same. With close coupling and sufficientquality of the resonant circuit, external influencing variables will nothave a very noticeable effect.

[0022] When a security device according to another embodiment of theinvention changes the frequency of the security signal cyclically intime between two limiting frequencies continuously or in steps anddetects its amplitude, the direction of change of amplitude of thesecurity signal will change largely at the same output frequency due tothe resonance frequency of the resonant circuit being exceeded. Thecorresponding frequency of the security signal or the relative timeperiod between the outputting of one of the limiting frequencies andsaid corresponding frequency can be a measure of a security signalinfluenced in the expected way.

[0023] When, in one of the two cases described by way of example above,the influencing means is removed, replaced by another influencing meansdiffering in impedance or coupling behavior or when the distance betweenthe coupling elements of the influencing means and the security devicechanges in any direction, this leads to a significant change ofresonance frequency and/or quality of the resonant circuit and/orcoupling factor. An evaluation means can therefore not recognize thesecurity signal influenced in the expected way.

[0024] Preferably, the security device can be calibrated for exampleafter the end of assembly of the data carrier system. This permitsphysical peculiarities of the specific influencing means and anypeculiarities of the relative position of security device andinfluencing means to be compensated. For example, the signal frequencyof a security signal can be calibrated in dependence on the actualresonance frequency or the actual frequency-dependent behavior of theinfluencing means, or the resonance frequency can be calibrated bycapacitances effective for the resonant circuit. Thus, significantfeatures of the detected-security signal can be adjusted as anevaluation criterion for the intactness of the security device, theinfluencing means and the part of the card body located therebetween.

[0025] In a preferred embodiment of an inventive data carrier system,the evaluation means tests two or more pieces of information that aredependent on the presence of a required influencing means. This permitsthe limiting values of the individual kinds of information, i.e. thepermissible deviations from the ideal value, to be selected with greatertolerance, or security to be increased with the same tolerance of saidlimiting values. Preferably, one of the kinds of information isdependent on the signal amplitude of the detected security signal, sothat not only the absolute presence of the influencing means but alsothe arrangement of the influencing means relative to the security deviceand thus to the chip with the security-relevant data can be consideredas an evaluation criterion in simple fashion.

[0026] When the permissible limiting values of the evaluation means aredefinable for such information dependent on the signal amplitude afterassembly of the data carrier system, said limiting values can benarrowly selected and a change of position of the influencingmeans-relative to the security device or a simulated influenced securitysignal will with high probability not lead to a detected security signalinfluenced in the expected way in the security device.

[0027] Another possible combination of security device and simple,passive influencing means provides for a delay unit, such as a stripline arrangement, as the influencing means. When a security devicerelated with the chip couples a pulsed signal of very high frequencycapacitively into such a delay unit and the detecting means capacitivelycouples out said signal phase-shifted by the delay unit, the phase shiftbetween coupled in security signal and coupled out security signal is asignificant feature for the presence of the undestroyed influencingmeans. The pulsed security signal can be pulse width modulated, pulsecode modulated or otherwise coded. The only essential thing is that thephase shift caused by the influencing means is detectable by a detectiondetection means. If the phase position between transmitted securitysignal and detected, i.e. received, security signal is not within anexpected range in such a data carrier system after attempted tampering,an evaluation means cannot recognize a security signal influenced in theexpected way.

[0028] If capacitive coupling of the security signal is provided, thisis preferably done between an electroconductive surface of the securitydevice on the chip or on a module firmly connected with the chip and anelectroconductive surface of the influencing means in the body of thedata carrier system. Thus, the relative position of influencing meansand chip immediately influences the coupling capacitance. If theinfluencing means is part of a resonant circuit or is a delay unit, thecoupling capacitance immediately influences the frequency-dependentbehavior of the influencing means: In addition, the coupling capacitancealso influences the amplitude of the transferred security signal withincertain limits.

[0029] A similar relation as for capacitive coupling also holds forinductive coupling, if an inductance of the security device forms aninductive transducer due to spatial association with an inductance ofthe influencing means. Here, too, the coupling factor, the quality andthe resulting inductance effective for the security device dependsignificantly on the position of the two inductances relative to eachother.

[0030] In particular in the case of high security requirements, theinfluencing means can be a transponder with active elements and anenergy coupling apparatus for transferring electric energy from the chipto the influencing means. In such a case, the simplest form of securitysignal can be a signal with alternating amplitude, such as a clocksignal, that guarantees the energy supply of such a transponder. Oneembodiment of such a transponder can deliver for example storedinformation. Said information can be transferred e.g. by load modulationof the security signal or by delivery of a transmit signal to thedetection means of the security device. In the case of load modulation,the security signal is immediately influenced by the transponder. In thecase of independent transmission of stored information, this influencingconsists in converting the security signal to a supply voltage anddelivering an independent information signal formed from said supplyvoltage.

[0031] Besides the presence of the information delivered by thetransponder, a delay time between commencement of the security signaland delivery of the information that is random for each transponder canbe provided for example as an evaluation criterion of the evaluationmeans.

[0032] In an especially favorable embodiment of an inventive datacarrier system, the evaluation criterion of the evaluation means can becalibrated to physical properties, such as a resonance frequency or adelay time of the influencing means. Thus, an influencing meanssimulated with fraudulent intent cannot cause an expected influencing ofthe security signal.

[0033] An especially secure embodiment of an inventive data carriersystem provides for an influencing means in the form of a transponderthat processes digital information in a security signal in a waypredictable only to the security device and transfers the result of saidprocessing to the security device. By transmitting random bit strings,the security device can tell by the detected result with certaintywhether the influencing means is still present in the original state.When an analog value component is additionally used as an evaluationcriterion in such a case, the original state of the data carrier systemcan also be tested. Besides a check of the amplitude or theroot-mean-square value of a detected signal received from theinfluencing means, a delay time can for example also be such an analogcomponent. For example, a capacitive coupling between security deviceand influencing means can be provided, the spatial arrangement of theinfluencing means relative to the security device defining the amount ofthe capacitance. Such a capacitance can be formed for example bycontactlessly overlapping metallic surfaces of the influencing means anda chip module containing the security device together with the bodymaterial located between said surfaces. Not only the superficial extentof the individual metallic surfaces but also the degree of overlapthereof, the distance between the surfaces and the electric constant ofthe body material located therebetween determine the capacitance. Eachspatial change of the position of said surfaces relative to each otherthus leads to a change of capacity. When a thus defined capacitance isused for example as the controlling factor for a delay time between anaction of the security device and a reaction of the influencing means,and the limiting values of said delay time are determined after thefinal assem-determined after the final assembly of the data carriersystem and adjusted in the evaluation means, tampering with the chip,the body material or the influencing means will lead with highprobability to an impermissible deviation of the signal detected by thedetection means that is recognizable to the evaluation means. A similareffect can also be achieved with inductive coupling.

[0034] For better signal coupling between the security device and theinfluencing means or also for reasons of energy saving, it isrecommendable to dispose the influencing means immediately adjacent tothe chip in the body of the data carrier system.

[0035] In the following the invention will be explained in more detailwith reference to the figures of the drawing, in which:

[0036]FIG. 1 shows a schematic block representation of a first specialembodiment of an inventive data carrier system;

[0037]FIG. 2 shows a schematic block representation of that part of asecond special embodiment of an inventive data carrier system thatdiffers from the embodiment according to FIG. 1; and

[0038]FIGS. 3A, B and C show schematic sectional views of a part of apossible form of realization of a data carrier system according to theembodiment from FIG. 2.

[0039] In the figures, the same reference signs designate the samefunctional units, and reference signs with the same reference numbersembodiments of the functional units with corresponding reference signs.

[0040]FIG. 1 shows data carrier system 1 with body 2 giving the datacarrier system its external form. Data carrier system 1 contains inknown fashion chip 16 and coupling apparatus 8 for permittinginformation exchange, for example a contact bank or antenna. The chip ofthe shown embodiment has microprocessor 15 that realizes control unit 3for controlling the functional routines of the data carrier system.Control unit 3 is connected via control and data bus 28 with read-onlydata memory 4 realized by a ROM, nonvolatile memory 5 realized by anEEPROM and working memory 6 realized by a RAM. Data and control bus 28is furthermore connected with input/output device input/output device 7permitting information exchange via coupling apparatus 8 with anexternal read/write device not shown in the figure. Input/output device7 can contain for example a voltage stabilizing device, a clockgenerating device and a driver arrangement depending on the kind ofinformation exchange and optionally the energy exchange via the couplingapparatus. In the case of contactless information exchange, a modem anda transceiver can also be provided in input/output device 7.Input/output device 7 is connected with coupling apparatus 8 viaconnection 29 for exchanging information and supply energy.

[0041] According to the invention, security device 9 is provided havingantenna 11 as the coupling unit of security device 9, transmitting unit10 for transmitting a security signal via antenna 11 and areceiver/demodulator as detection means 12. Antenna 11 is connected viasecurity signal line 21 with transmitting unit 10 and detection means12. Transmitting unit 10 and receiver/demodulator 12 are integrated inchip 16 in the shown embodiment and controlled by control unit 3 forcontrolling the functional routines of data carrier system 1. Detectionmeans 12 is connected via connection 22 for transferring the detected,influenced security signal with evaluation means 13 realized bymicroprocessor 15. Evaluation means 13 is connected via connection 23for transferring the evaluation result with blocking means 14, which islikewise realized by microprocessor 15. Blocking means 14 transfersblocking information via connection 24 to control unit 3 of the datacarrier system. Connections 23 and 24 are shown primarily forillustrating the information flow between functional blocks 13, 14 and3. The actual information flow takes place in the usual way withinmicroprocessor 15.

[0042] Body 2 also contains influencing means 17 having antenna 18 asthe coupling unit of influencing means 17. Antenna 18 is connected viasecurity signal line 26 with radiofrequency unit 19, which is in turnconnected via information line 27 with signal influencing control 20. Inthe shown embodiment of FIG. 1, signal influencing control 20furthermore has delay timer 20a whose time constant is determined in away not shown by a capacitance that depends on the arrangement ofinfluencing means 17 in body 2. Signal influencing control 20 exchangesinformation with radiofrequency unit 19 via information line 27.

[0043] Radiofrequency unit 19 of influencing means 17 contains, in theway known for RFID transponders, a voltage regulating device forproducing a supply voltage for influencing means 17 from a securitysignal received via nongalvanic coupling 25. Radiofrequency interface 19furthermore contains a modulator unit for influencing a receivedsecurity signal and a receiving unit for receiving and demodulating thesecurity signal.

[0044] Signal influencing control 20 defines the manner of influencing asecurity signal received from security device 9. This could be realizedin simple embodiments of an inventive data carrier system by deliveringa predetermined stored information content, dispensing with a receivingunit of radiofrequency unit 19. In the present embodiment, however,information received from security device 9 is processed according to apredetermined algorithm and the processing result transferred toradiofrequency interface 19, which in turn modulates the reflectioncross section of antenna 18 by load modulation.

[0045] Body 2 in the shown embodiment corresponds to the body of a chipcard. Mask ROM 4 serves to store the standard commands of the operatingsystem of the chip of said chip card. Nonvolatile memory area EEPROM 5serves to store specific operating system commands and store additionalprogram codes. Furthermore, EEPROM memory 5 serves as a data memory, forstoring security-relevant data, among other things. Thesecurity-relevant data are protected by hidden addressing and can thusnot be spied out.

[0046] Working memory 6 is a volatile memory and all information storedin said memory is lost when the supply voltage is switched off.Preferably, a memory is used having self-erasing memory cells, whichimmediately erase the memory content when the supply voltage is stopped,by switching the storage capacities of the individual memory cells to afixed potential. When coupling apparatus 8 is a contact bank of acontact-type chip card, input/output device 7 contains a register withdrivers for transferring data bit-by-bit.

[0047] In operation, i.e. when such a chip card is inserted into areader, chip 16 is supplied with energy via coupling apparatus 8 andconnection 29, and control unit 3 causes required data, includingsecurity-relevant data, to be taken over from nonvolatile data memoryEEPROM 5 to working memory RAM 6. Before security-relevant data aretaken over from the EEPROM to working memory 6, control unit 3 causestransmitting unit 10 to transmit a security signal via security signalline 21 and antenna 11. Said security signal contains a pseudo-randombit string that is also made available to evaluation means 13. Thesecurity signal radiated by antenna 11 is received by antenna 18 ofinfluencing means 17 and passed on via security signal line 26 toradiofrequency unit 19. Radiofrequency unit 19 creates from the clock ofthe security signal a supply voltage for influencing means 17 anddemodulates the security signal to extract the pseudo-random bit stringand transfer it via information line 27 to signal influencing control20. Upon the first occurrence of a security signal on antenna 18,radiofrequency unit 19 furthermore sets delay timer 20A to start a delaytime.

[0048] Signal influencing control 20 applies to the bit string of thesecurity signal an algorithm specific to this specific chip card togenerate an influencing signal. Evaluation means 13 applies the samespecific algorithm to the bit string of the security signal and thuslikewise determines the influencing signal.

[0049] Signal influencing control 20 transfers the influencing signaldetermined thereby via information line 27 to radiofrequency unit 19,which in turn modulates the reflection cross section of antenna 18 withthe influencing signal by load modulation. Said backscatter modulationon antenna 18 permits a receiver/demodulator contained in detectionmeans 12 to detect the influenced security signal via antenna 11 andsecurity signal line 21 and demodulate the influencing information. Theinformation detected and extracted by detection means 12 is transferredvia connection 22 to evaluation means 13, where it is compared with theinformation determined in evaluation means 13. If any deviationsdetermined by evaluation means 13 between the influencing informationdetected by detection means 12 and the influencing informationdetermined in the evaluation means are within a permissible tolerancerange, the relevant part of the influenced security signal is consideredrecognized. If the influencing means has been removed or replaced byanother similar influencing means, the evaluation means means, theevaluation means will not be able to determine said expected influencinginformation.

[0050] Radiofrequency interface 19 of influencing means 17 begins withload modulation only when delay timer 20A transfers a correspondingstart signal to the radiofrequency interface after expiration of anindividual delay time. Preferably, the time constant of delay timer 20Adepends on the position of influencing means 17 relative to antenna 11and/or to chip 16. Thus, the relative position between influencing means17 and security device 9 is essential for the time period between thereception of a security signal by radiofrequency interface 19 and thestarting of load modulation by radiofrequency interface 19.

[0051] Evaluation means 13 stores a delay time tolerance range specificto this particular chip card, which has preferably been determined aftercompletion of the chip card. Evaluation means 13 compares the timeperiod between delivery of a security signal via antenna 11 anddetection of influencing information by detection means 12 with saiddefined tolerance range. If said time period is within the statedtolerance range, this part of the influenced security signal is alsoconsidered recognized. If influencing means 17 or chip 16 has beenremoved, even if the data carrier system was subsequently reassembled,there will be a change in the time constant defined by the arrangementof influencing means 17 and chip 16 or antenna 11. Thus, the evaluationmeans will not be able to determine said expected influencinginformation.

[0052] If the influencing information has an excessive error raterelative to the information determined in evaluation means 13, or if thetime between delivery of a security signal and reception of influencinginformation is not within the predetermined tolerance range, evaluationmeans 13 passes blocking information to blocking means 14 to preventblocking of the transfer of security-relevant data from EEPROM 5 toworking memory 6.

[0053] In addition, the blocking information that blocking means 14transfers to control unit 3 can also cause erasure of working memory 6.

[0054] In an especially favorable embodiment of such a portable datacarrier system, the time constant of delay timer 20A is only startedwhen certain start information transmitted by control unit 3 isdetermined in RF interface 19. Thus, the delay time is no longerimmediately dependent on the easily determined turn-on time ofinfluencing means 17.

[0055] The embodiment according to FIG. 1 relates to portable datacarrier system 1 with relatively complicated security device 9 andaccordingly complicated influencing means 17 to guarantee a highsecurity standard. In contrast, the embodiment according to FIGS. 2 and3 relates to a data carrier system with simply realized influencingmeans 17 and simply realized security device 9. The data carrier systemaccording to FIGS. 2 and 3 is based on a system according to FIG. 1, sothat FIGS. 2 and 3 only show functional units essential for thedifferent mode of functioning of the embodiment.

[0056]FIG. 2 shows control unit 3 for controlling the functionalroutines of the data carrier system, which is in operative connectionvia data and control bus 28 with EEPROM memory 5 and working memory 6 aswell as oscillator 10A provided as a transmitting unit for delivering asecurity signal. Two output terminals of oscillator 10A are connectedvia security signal line 21 to input terminals of voltage detector 30and to electroconductive surfaces 11A and 11B that together formcoupling unit 11 of the security device. Electroconductive surface 11Aforms together with electroconductive surface 18A of influencing means17 a capacitance. Electroconductive surface 11B also forms together withelectroconductive surface 18B of influencing means 17 a capacitance.Electroconductive surfaces 18A and 18B of influencing means 17 areinterconnected via inductance 39, so that oscillator 10A is loaded witha series resonant circuit comprising the series circuit of capacitances11A with 18A, 11B with 18B as well as inductance 39. The outputamplitude of oscillator 10A depends very greatly on the deviation of theresonance frequency of stated resonant circuit 11A, 18A, 11B, 18B, 39and the oscillator frequency of oscillator 10A. Said voltage detector30, which is preferably a high-impedance root-mean-square valuerectifier or peak value rectifier, forms together with analog-digitalconverter 31 detection means 12A with a digital signal output. Theoutput of detection means 12A is connected via connection 22 fortransferring the detected, influenced security signal with windowcomparator 13A pro- with window comparator 13A provided as theevaluation means. Window comparator 13A compares whether the outputsignal of analog-digital converter 31 and thus the oscillation amplitudeor the mean voltage at the output of oscillator 10A is within apredetermined tolerance range. Window comparator 13A transfers theresult of comparison via connection 23 to blocking means 14, whichtransfers blocking information to control unit 3 via connection 24depending on the result of comparison. The tolerance range of windowcomparator 13A is preferably defined after completion of a data carriersystem according to FIG. 2 with consideration of permissible deviationsdue to external influences.

[0057] Since the capacitances of the resonant circuit formed fromcoupling unit 11 and influencing means 17 are greatly dependent on theposition of metallic surfaces 11A and 18A or 11B and 18B relative toeach other, tampering with the data carrier system, in particulardestruction of influencing means 17 or removal and reinsertion ofinfluencing means 17, will lead with high probability to a strongdeviation of the resonance frequency of resonant circuit 11A, 18A, 11B,18B, 39 loading oscillator 10A. This has great effects on the outputsignal amplitude of oscillator 10A due to the strong frequencydependence of the impedance of a resonant circuit. Thus, windowcomparator 13A provided as the evaluation means can detect tamperingwith coupling unit 11 of the security device or with influencing means17 with very high probability and accordingly cause blocking means 14 todeliver a blocking signal via connection 24.

[0058]FIGS. 3A, 3B and 3C show sectional views through card body 2 inthe area of the security device and the influencing means. Inparticular, an especially favorable influencing means is shown. FIG. 3Ashows a portion of body 2 that is part of a contact-type chip card. Inparticular, a section along line x-x shown in FIG. 3B is depicted. FIG.3A shows inductance 39 disposed between two metallic surfaces 18A and18B. Said inductance can be formed as the metalized reflecting surfaceof hologram 40, as recognizable in FIG. 3B in the sectional view alongcutting line y-y shown in FIG. 3A.

[0059]FIGS. 3B and 3C show sections through a contact-type chip cardalong cutting lines y-y and z-z shown in FIG. 3A. Said chip cardconsists of card body 2 with out-side, preferably transparent card layer32 shown on the top, inside card layer 33 receiving hologram module 40,inside card layer 34 adjacent thereto and receiving the chip of a chipcard module, and outside card layer 35 shown at the bottom. Outside cardlayer 35 shown at the bottom receives carrier foil 37 of a chip modulewith external contacts 8A of a contact bank. The chip module consistingof carrier foil 37, external contact bank 8A, chip 15, adhesive foil 38,electroconductive surfaces 11A and 11B, chip cover 36 and connectionwires 21 and 29 is so disposed below hologram module 40 that metallicsurface 18B of the hologram module is disposed at a predetermineddistance and with predetermined overlap relative to metallic surface 11Bof the chip module, and metallic surface 18A of the hologram module isdisposed accordingly opposite metallic surface 11A of the chip module torealize capacitors.

[0060] When the chip module or the metallic surface of hologram 40 isdetached from the card with such a constellation of chip module andinfluencing means 17, no resonant circuit is applied to the output ofoscillator 10A shown in FIG. 2. Accordingly, the output amplitude ofoscillator 10A is very small compared with the output amplitude of theoscillator when loaded with a resonant circuit tuned to the oscillatorfrequency. Window comparator 13A in FIG. 2 can thus easily detect theabsence of such a resonant circuit.

[0061] Even if metalization layer 18A, 18B, 39 of hologram module 40 orthe chip module is subsequently reinstalled, the degree of overlap ofcapacitor electrodes 11A and 18A or 11B and 18B will with highprobability no longer match the original degree of overlap. Furthermore,the distance between said capacitor electrodes will with highprobability not be identical with the original distance. Consequently,the resonance frequency of the resonant circuit formed by subsequentassembly of the individual components of the data carrier system willnot be identical with the resonance frequency of the original system.Such tampering with inventive data carrier system 1 will also beaccordingly recognized by window comparator 13A, and blocking means 14can cause blocking of a security-relevant function by control unit 3.

1. A portable data carrier system having a control unit, a body giving the data carrier system its external form, a means for permitting information exchange between the control unit and an external access unit, and a data memory integrated in a chip, in which security-relevant data can be stored, a security device for transmitting a security signal, an influencing means integrated in the body and connected with the security device for influencing the security signal, a detection means of the stated security device for detecting the security signal influenced by the influencing means, an evaluation means for evaluating the detected, influenced security signal, and a blocking means for blocking a security-critical operating state of the data carrier system if the evaluation means does not recognize a security signal influenced in the expected way, characterized in that the security device is connected non-electrically with the influencing means, the transmitted security signal contains a bit string as the information, and the influencing means is designed to transmit a bit string altered from said bit string in a way predictable for the evaluation means to the detection means.
 2. A data carrier system according to claim 1, characterized in that the detection means and the evaluation means are integrated at least partly in the chip, and the evaluation criterion of the evaluation means is an influenceable component of the security signal that depends significantly on the position and/or distance of the influencing means relative to at least one component of the security device.
 3. A data carrier system according to claim 1, characterized in that the influencing means is a passive electric circuit effective in the radiofrequency range and causing frequency-dependent influencing of the security signal.
 4. A data carrier system according to claim 1, characterized in that the influencing means comprises at least partly of a metal layer in the body.
 5. A data carrier system according to claim 3 4, characterized in that the influencing means is a resonant circuit .
 6. A data carrier system according to claim 1, characterized in that the influencing means is a transponder device.
 7. A data carrier system according to claim 1, characterized in that the influencing means utilizes a metallic layer of an optically perceptible security feature.
 8. A data carrier system according to claim 1, characterized in that the transponder device is supplied with energy by the security device.
 9. A data carrier system according to claim 1, characterized in that the evaluation means can be calibrated to physical properties of the influencing means.
 10. A data carrier system according to claim 9, characterized in that the security signal is a clock signal for energy supply of the transponder device.
 11. A data carrier system according to claim 10, characterized in that the transponder device delivers stored information after being supplied with energy by the security signal.
 12. A data carrier system according to claim 1, characterized in that the security device and thus the security signal transmitted thereby can be calibrated.
 13. A data carrier system according to claim 1, characterized in that the amplitude of the detected, influenced security signal is provided as the evaluation criterion for the evaluation means.
 14. A data carrier system according to any of the claim 1, characterized in that the influencing means is disposed immediately adjacent to the chip in the body. 